Removal of UV-cured resin using a hybrid cleaning process for nanoimprint lithography Min-Su Kim a , Bong-Kyun Kang a , Manivannan Ramachandran a , Jae-Kwan Kim b , Byung-Kyu Lee b , Jin-Goo Park a,⇑ a Department of Bio-Nano Technology and Material Science Engineering, Hanyang University, Ansan 426-791, Republic of Korea b SAIT, Samsung Electronics, 14-1 Nongseo-dong, Yongin 446-712, Republic of Korea article info Article history: Available online xxxx Keywords: UV-cured resin removal UV/O 3 pretreatment DIO 3 cleaning Megasonic abstract Removal of resin residues from quartz surfaces is one of the most critical issues in ultraviolet (UV) nanoimprint lithography (NIL) processes. Traces of resin residues on a quartz stamp cause pattern defects in the subsequent UV NIL process. This study investigates the effect of UV/O 3 pretreatment and ozone dis- solved water (DIO 3 ) cleaning with megasonic (MS) on UV-cured resin removal. The bulk resin was oxi- dized and removed partly by UV/O 3 pretreatment. The resin residues which remained on the surface in the form of a thin layer were removed by cleaning with 40 ppm DIO 3 along with megasonic. Subse- quently, cleaning was performed using a 10% KOH solution to remove the adhesion promoter. Contact angle measurements showed that the surface was hydrophilic in nature, which confirms the complete removal of the UV-cured resin and adhesion promoter from the SiO 2 substrate. Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction Lithography is one of the key technologies used in semiconduc- tor fabrication processes. Several lithography processes such as ex- treme ultraviolet (EUV) lithography and nanoimprint lithography (NIL) have been developed to generate nanoscale patterns. Among them, NIL is known as a low-cost and simple method to fabricate nano-sized patterns [1]. In NIL technology, ultraviolet nanoimprint lithography (UV-NIL) makes it possible to fabricate 3-dimensional patterns. As this technique operates at a low pressure and low tem- perature [2], UV-NIL has great potential as a new manufacturing process. However, the UV-NIL process uses an expensive quartz substrate for the transmission of UV light. When a nano-sized pat- tern is duplicated from a quartz mold to a Si substrate, pattern de- fects occur not only by particle contaminant but also from resin residues which exist on the quartz pattern mold. Therefore, a con- tamination-free quartz mold is needed. Usually, UV-NIL uses UV-curable resins, whose chemical bond- ing and structure may be altered during UV light exposure result- ing in crosslinking between the polymers. This UV-cured resin mold with a crosslinking structure is very hard to remove from quartz substrates [3]. Conventionally, sulfuric acid-peroxide mix- ture (SPM) was used to remove the UV-cured resin. However, SPM cleaning process cannot remove the particles completely and also leads to haze formation on the wafer. Hence, APM cleaning is always performed after SPM cleaning [4]. In general, APM cleaning is performed at 60 °C and the etch rate of SiO 2 is about 1 Å/min [5]. However, it may affect the nano-sized pattern of the quartz stamp during APM cleaning for recycling quartz stamp. Several cleaning methods such as using UV/O 3 and DI water containing dissolved O 3 (DIO 3 ) have been applied for the removal of a cross-linked ion implanted photoresist [6–8]. The UV/O 3 clean- ing process in which ozone is generated from oxygen by UV light is effective for photoresist removal [9]. On the other hand, DIO 3 -as- sisted photoresist stripping and organic contaminant removal rely on direct or indirect oxidation reactions [10]. DIO 3 is a well-known powerful oxidizer for the removal of organic contaminations and is also an environmental friendly solution [11]. However, there have been no studies reported in the literature regarding the applicabil- ity of these cleaning techniques for the removal of UV-cured resin from quartz substrates. Hence, in this study, we investigated the performance efficien- cies of both UV/O 3 and DIO 3 with megasonic (MS) cleaning tech- niques on the removal of UV-cured resin from quartz. The optimum conditions to improve the resin removal efficiency are suggested based on detailed experimental investigations. 2. Materials and methods A schematic representation of the UV-cured resin structure is shown in Fig. 1. In this work, we used SiO 2 surfaces instead of a quartz surface because they are much cheaper. An adhesion 0167-9317/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.mee.2013.05.005 ⇑ Corresponding author. Tel.: +82 31 500 5226; fax: +82 31 400 4729. E-mail address: jgpark@hanyang.ac.kr (J.-G. Park). Microelectronic Engineering xxx (2013) xxx–xxx Contents lists available at SciVerse ScienceDirect Microelectronic Engineering journal homepage: www.elsevier.com/locate/mee Please cite this article in press as: M.-S. Kim et al., Microelectron. Eng. (2013), http://dx.doi.org/10.1016/j.mee.2013.05.005